Abstract
The groundwater of Awe-Keana saline fields in central Nigeria was studied to investigate physicochemical processes that influence its groundwater chemistry and quality and hence determine its quality for drinking and irrigation purposes. Twenty groundwater samples were collected from hand-dug wells and boreholes for the purpose of identifying the hydrochemical characteristics and assessing the quality of groundwater of the Awe-Keana saline fields. Principal component analysis was performed to identify the hydrochemical controlling processes while water quality index (WQI) was used to determine the overall quality of the water samples. Multiple regression analysis, however, revealed the parameter(s) that impact the overall water quality the most. The results showed that the chemical compositions of the groundwater of the area is influenced by weathering of hostrocks, salinity and anthropogenic activities. Four hydrochemical facies were deciphered (Ca-Mg-HCO3, Na-K-HCO3, Na-K-Cl-SO4, and Ca-Mg-Cl-SO4) and this revealed the diversity in the chemical controlling processes that yield different facies. Two clusters of water groups were identified from cluster analysis, namely, groundwater characterized with very high salinity, high nitrate contamination and high Ca, Cl, Na, and HCO3 ionic concentrations and groundwater with high Mg, K, and SO4 ionic concentrations. Saturation indices in relation to different minerals showed that precipitation and dissolution processes gave rise to the concentrations of different ions in the groundwater. Water quality assessment showed that about 85 % of the groundwater of the area is unsuitable as drinking water but, generally suitable for irrigation. Multiple regression analysis revealed that NO3 ion among the hydrochemical parameters measured was observed to be the major pollutant in the groundwater of the study area.
Highlights
Introduction the sedimentary basinDifferent hypothesis has been given toThe Awe – Keana saline fields is located in parts of the Central Benue Trough (CBT), Nigeria
Awe-Keana brine fields are known to have very strange and difficult hydrogeological situations. These conditions arise from the fact that most of the potential aquifers are either limited in extent, thinly developed with consistent clay and shale interbeddings or even highly indurated that only the development of secondary voids created by fractures, joints and solutions channels can attract hydrogeological interest
The Awe-Keana saline field of the CBT is underlain by the following geological sequence: the Asu River Group, the Ezeaku, the Keana/Awe Formation the Awgu Formation and the Lafia Sandstone
Summary
Awe-Keana lies within latitudes 8◦06 N to 9◦ 09 N and longitudes 8◦ 47 E to 9◦ 09 E. Massive outcrops occur at Keana, Azara and Daudu This was followed by the Awe Formations which was deposited as passage. The post-folding Campano-Maastrichtian Lafia Formation ended the sedimentation in the Middle Benue Trough, after which widespread volcanic activities took over in the Tertiary It is lithologically characterized by ferruginized sandstones, red, loose sands, flaggy mudstones, clays and claystones. Awe-Keana brine fields are known to have very strange and difficult hydrogeological situations These conditions arise from the fact that most of the potential aquifers are either limited in extent, thinly developed with consistent clay and shale interbeddings or even highly indurated that only the development of secondary voids created by fractures, joints and solutions channels can attract hydrogeological interest. Awe Formation aquifer is the lowest aquifer and is composed of series of shale and porous sandstone beds and is highly productive. The presence of salt in it renders it unfavourable for groundwater exploration as the water from wells tapping the aquifer around Old Awe Town (Tsohon Gari) show high saline concentration because of the out-cropping brinebearing Awe Formation [14]
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